1. Field of the Invention
The present invention relates to a depth stop assembly for rotatable and/or percussion hand-held power tools such as hand-held drilling tools or hammer drills for forming blind bores, in particular, in stone, in which fastening elements are received. The present invention also relates to a fastening element to be inserted in a bore produced with a hand-held tool equipped with the depth stop assembly, and to a method of adjusting the position of the depth stop assembly.
2. Description of the Prior Art
In many applications, a precise depth of a blind bore has to be provided in order to insure an optimal anchoring of a fastening element subsequently placed into the blind bore. To this end, the removal of the material from a bottom of the blind bore should stop at a predetermined penetration depth.
The establishing of a predetermined depth of a blind bore can be achieved by ending the rotational or percussion movement and/or by ending the advance of the working tool. The advance can be rerouted to another location on the constructional component.
For limiting the penetration depth, U.S. Pat. No. 4,890,779 discloses the use of special setting tools which are inserted in the chuck of a hand-held tool and which are provided with a depth stop. The drawback of this special setting tools consists in their limited application, as they are intended for use in limited specific cases.
U.S. Pat. No. 3,633,682 discloses a depth stop for drill hammers and formed as a deflection-resistant, rod-shaped, depth-setting member displaceable along the tool axis. Advantageously, the depth stop is mounted on an auxiliary handle of the hand-held tool. A mechanical contact of the depth-setting member with a constructional component, primarily a wall, simply and effectively prevents further penetration of the working tool beyond the depth predetermined by the depth stop. The drawback of the depth stop disclosed in U.S. Pat. No. 3,633,682 consists in that the depth stop is adjusted manually and, thereby, is error prone.
According to U.S. Pat. No. 4,436,460, for forming a bore in a cylinder, the position of the working tool is measured and evaluated. This stand-dependent special case is not applicable to hand-held tools.
U.S. Pat. No. 4,717,291 discloses a depth stop for a hand-held tool and which includes a non-rotatable, sleeve-shaped stop displaceable along the tool axis. The position of the stop is adjusted, in accordance with the working tool length, by a depth controlling unit provided with a screw gear. A mechanical contact with the constructional component interrupts the penetration of the working tool. The drawbacks of this depth stop consist in the required sleeve shape of the stop member which surrounds the working tool, and in having a need to provide a screw gear having increased dimensions.
WO 86/03314 discloses use of labels having a bar code for identification. WO 86/02186 discloses the use of passive film resonant circuits for identification. WO 89/05984 discloses the use of an externally driven active transponder for identification. The use of bar-coded labels, resonant circuits, transponders for identification, for answering inquiries, for storing data is well known, and they can be produced in large number in mass production. An object of the present invention is a depth stop assembly for a hand-held power tool with which, during boring of a blind hole for receiving a fastening element, the hole depth is limited to a value associated with the length of the fastening element.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a depth stop assembly including a rod-shaped, deflection-resistant, depth-setting member supported for a limited movement parallel to an axis of the power tool and adjustable in accordance with a stop length associated with a fastening element insertable in the blind bore, a motorized control module associated with the depth-setting member and connectable with an energy source, a length-determining sensor associated with the depth-setting member, a transceiver unit for contactless reading of an identification of identification means connected with the fastening element, and a micro-controller for controlling operation of the control module and connected with the transceiver unit and the sensor to provide for adaptive adjustment of the stop length. Thereby, the blind bore depth is limited in accordance with the stop length.
Advantageously, the control module is formed as a step motor on the output shaft of which, a worm gear, which cooperates with a rack that forms part of the depth-setting member, is supported.
The length-determining sensor is advantageously formed as a magnetic sensor for determining a total length or is formed of a plurality of incremental magnetic strips characterizing the length of the depth setting member.
Advantageously, the identification means is formed as a bar code, film resonant circuit, or a transpoder and is located on or in the fastening element in an unimportant, for its functioning, location. In addition to data indicating the blind bore depth, the indentification means can contain other data such as a blind bore diameter, length of the working tool, or the type of the working tool. All of the data are displayed on a display which is controlled by micro-controller and which is provided on a housing containing the transceiver unit and the micro-controller. The transceiver is formed in accordance with the type of the identification means and can be formed as a laser scanner/light receiver unit, a radio transceiver, or a radio transceiver with a modulated carrier frequency.
Advantageously, the depth stop assembly is mounted adjacent to the chuck of a hand-held tool and, advantageously, is secured with appropriate attachment means on an auxiliary handle of the hand-held tool.
Advantageously, the depth stop assembly is connected with the energy source, which is integrated in the hand-held tool, by a sliding or plug contact provided in the region of the attachment of the depth stop assembly in vicinity of the chuck or by a flexible conductor with a plug connector. As energy source, advantageously, a battery, an accumulator, or a storing capacitor can be used, which, advantageously, is integrated in the auxiliary handle of the hand-held tool.
Advantageously, the energy source, which is formed as an accumulator or a storing capacitor, is connected, by a power converter, with a coil formed as a secondary winding of transformer and through which a magnetic flux is generated by a coil formed as a primary winding, passes. The primary coil represents a part of the electrical drive of the hand-held tool and can be formed, e.g., as a stator winding. Such an arrangement insures an appropriate energy supply of the depth stop assembly.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof,.will be best understood from the following detailed description of preferred embodiment, when read with reference to the accompanying drawings.